1. Field of the Invention
The invention relates to a light emitting diode and a data transmission and reception apparatus, and particularly relates to a light emitting diode and a data transmission and reception apparatus suitable for visible light communications (VLC).
2. Description of Related Art
Since light emitting diodes (LED) are more and more commonly used for illumination nowadays, the potential of LED in the field of visible light communications (VLC) has drawn people's attention due to its characteristic of high-speed modulation. For example, the visible light emitted by one or more LEDs may serve to transmit data in a VLC system.
However, it is still challenging to use the conventional white LEDs in the field of VLC. The conventional white LEDs may be categorized into two types, one is the phosphor white light emitting diodes, and the other is the white light emitting diodes using red, green, and blue light emitting diode chips. The conventional phosphor white light emitting diode includes a blue light emitting diode and a yellow phosphor. The blue light emitting diode emits blue light to excite the yellow phosphor, and the yellow light emitted by the yellow phosphor after the yellow phosphor absorbs a portion of the blue light is combined with another portion of the blue light to form the white light. In general, the light emitting mechanism for the phosphor to be excited by light is termed as phosphorescence. The lifetime of phosphorescence is approximately in a range from 10−3 to 102 seconds, and the modulation bandwidth of the light emitted by phosphor is limited, normally not exceeding 10 Mbps. Thus, it is rather difficult to use the phosphor white light emitting diode as a high-bit-rate data transmitter in a VLC system.
Compared with the phosphor white light emitting diode, the overall modulation bandwidth of the white light emitted by the white light emitting diode formed by the red, green and blue light emitting diode chips is not influenced by the phosphor having a slower responding speed and able to provide a higher modulation bandwidth. Thus, such white light emitting diode may be used as a high-bit-rate data transmitter and an illumination device. However, from the perspective of cost, such white light emitting diode is formed by three different light emitting diodes (i.e., red, green, and blue light emitting diodes), so it requires more light emitting diodes and more kinds of light emitting diodes. Thus, the driving circuit thereof is more complicated, and the cost thereof is also higher. Furthermore, since the three kinds of light emitting diodes have different life time, after the white light emitting diode is used for a while, the light output of the white light in terms of color temperature and power is changed to differ from the initial state. As a result, color sensors and feedback circuits need to be used to correct the white light output, and the initial driving condition needs to be changed, so as to achieve the initial color temperature of the white light of the white light emitting diode.
Thus, developing a low-cost light emitting diode suitable for the VLC system is certainly an issue for researches to work on.